The calculation of the discrete cosine transform (DCT) of a pixel matrix of a picture is a fundamental step in processing picture data. A division by a quantization matrix is performed on the results of the discrete cosine transform for reducing the amplitude of the DCT coefficients, as a precondition to data compression which occurs during a coding phase, according to a certain transfer protocol of video data to be transmitted or stored. Typically, the calculation of the discrete cosine transform is carried out on blocks or matrices of pixels, in which a whole picture is subdivided for processing purposes.
Increasing speed requisites of picture processing systems for storage and/or transmission, imposes the use of hardware architectures to speed up various processing steps among which, primarily, the step of discrete cosine transform calculation by blocks of pixels. Use of hardware processing imposes a pre-definition of few fundamental parameters, namely the dimensions of the blocks of pixels into which a picture is subdivided to meet processing requisites.
Such a pre-definition may represent a heavy constraint that limits the possibility of optimizing the processing system, for example a MPEG2 coder, or its adaptability to different conditions of use in terms of different performance requisites. It is also evident the enormous economic advantage in terms of reduction of costs of an integrated data processing system that may be programmed to calculate in parallel the DCT on several blocks of pixels of size selectable among a certain number of available sizes.